Engine governors



April 2, 1963 A. G. WALFORD ENGINE GOVERNORS Filed Nov. 7, 1958 I n uenlo r 1425mm? fame )Zyzmw A ltorneys 3383,59? ENGINE GQVEE Q @123Alexander G. Walford, Colchester, England, assignor to Darcy, l arman Srflompzmy Limited, olchesten England Nov. 7, -953, Ser. No. 772,571Qlaims priority, application Great Britain Nov. 12, 1957 This inventionrelates to engine governors designed to control the speed of an engineunder varying conditions of load and in particular to a centrifugalfiyweight governor of the servo-operated type utilizing fluid-pressurefeedback on to the main pilot valve sleeve or, preferably, on to themain pilot valve itself.

According to the invention, means is provided for varying the steadystate feedback pressure to vary the equilibrium speed of the governor soas to obtain any desired value of permanent speed droop (i.e. apredetermined speed variation in proportion to applied load). Means isalso provided for adjusting the governor to give isochronous runningwhen desired.

An embodiment of the invention will now be described with reference tothe accompanying drawing. In this embodiment, the feedback is on to themain pilot valve.

The basic governor comprises two units. These may be mounted together orseparately with pipe connections (shown dotted). The two units are (a)the speed sensing and oil supply unit on the left, and (b) the powerunit on the right.

Unit (a) is the larger of the two units and is mounted vertically. Itcontains the fiyweights 4, spring drive as sembly 3, pilot valve 9, oilpump 11, hydraulic accumulator 16 loaded by springs 17, speed settingmechanism 1 and 2 and the oil storage reservoir.

The fulcrum bearings 7 of the conventional flyweights 4- are of theneedle roller type to minimize friction. The fiyweight force istransmitted to the speeder spring 3 by an angular contact ball race andspring carrier 5. The pilot valve 9 moves inside a sleeve 1% whichrotates with respect to it to minimize friction. The oil pump 11 is ofthe gear type and is driven together with the governor from a driveshaft 13 by a set of change-speed gears 12 for speed adjustment. Thedrive shaft 13 runs in bearings 14 and is provided with an oil seal 15.All the Working parts are immersed in oil except the fiyweight systemand spring drive.

The speed sensing and oil supply unit also comprises a feedback receiverhaving a fioating spring-loaded pisto 18 in a cylinder, the force fromspring 2% being transmitted through a point contact strut 19 so thatlateral forces are minimized.

Unit (1)) comprises the power piston 22, feedback transmitter elementsand integral action control valve 40.

The power piston 22 which operates the mechanism for taking thenecessary corrective action is of the differential area type, thuseliminating a return spring within the governor. (A return spring toperform the required duty at the pressures involved would be ofexcessively large proportions.) The difierential areas of the piston areso arranged that the return force is 75% of the force to increase fuel.This allows a return spring giving a force equivalent to 25 of thegovernor force to be fitted on the external linkage acting in thedirection to reduce fuel in order to eliminate backlash.

The basic droop piston 39 and the spring guide 26 of the permanent droopcontrol valve 29, which is of the spring-loaded ball-type, aremechanically connected to the power piston 22. by an adjustable linkage59, allowing the amounts of basic and permanent droop to be varied tosuit requirements. The piston 39 is operated niteti rates atone from alever 44- connected to the piston rod passing through a bushing 38.

The fulcrum 4-1 of the lever 25 connected to the permanent droop controlvalve can be moved bodily to vary the amount of movement given to thecontrol valve by a given movement of the power piston. In one positionof the fulcrumin line with the central axis of the valve 29 and itsspring 27this movement is reduced to zero. This is for isochronousoperation as will appear later.

The means for moving the fulcrum 41 include an adjusting screw 31rotatable by a knob 36. Similar means is provided for adjusting thefulcrum 3d of lever 44. This means comprises a fulcrum bracket 33 whichcan be moved relative to a slide 32 by rotating an adjusting screw 47 bymeans of a knob 37. A friction adjustment is provided in the form of anut 35.

A load sensing unit (not shown) may be added to the governor at 42 todecrease the frequency variations on an alternator set. A solenoid,energized from a wattmeter circuit in the alternator output, controlsthe movement of a pilot valve which in turn controls a piston in thefeedback circuit. Displacement of this piston created by a change inalternator load in turn causes a movement of the power piston, varyingthe engine power output to suit the power required. This action willprecede a speed variation and will greatly reduce temporary variationsof frequency during load changes.

As applied to this embodiment the operation of the load sensing unit isas follows.

The input to the solenoid corresponds to the load on the prime-mover,thus deflecting the solenoid core and pilot valve controlled therebyagainst a spring. This admits oil to the space above the piston of theload sensing unit (or drains it) depending upon the variation of load.The displacement of this piston causes a corresponding movement of thesleeve of the speed sensing unit and movement of the power piston. Themovement of the power piston causes a corresponding movement of thebasic droop piston, until the displacement of this piston cancels outthe movement of the load sensing unit piston, restoring the sleeve toits original position and causing movement to cease. In practice, due tothe time delays in the system, exact follow up of the power piston toload change does not occur and a small variation of speed takes place.The speed sensing system corrects this in the normal way.

It is to be understood that the load sensing unit need not beelectrically operated nor indeed is its presence in any way essential tothe working of the invention.

The operation of this embodiment will now be de scribed under variousworking conditions.

Increase of Load (lsochronous Setting) An increase in load causes thespeed of the prime mover to drop. The fiywe-ights 4 move inwards becausethe force exerted by the speeder spring 3 overcomes the force exerted bythe flyweights. This causes the pilot valve 9 to move downwardsresulting in a flow of high pressure oil past the control land of thepilot valve and through connection 43 to the underside of the powerpiston 22 causing it to move upwards and increase the fuel supply to theprime mover by rotating the control shaft 21. Cont-r01 shaft 21 whichrotates with lever 23 connected to piston 22 may be operativelyconnected for example by linkage 51 to a suitable throttle valveassembly 52 disposed in a fuel conduit 53 for supplying more fuel to theprime mover. This upward movement of the power piston causes a downwardmovement of the basic droop piston 39 via the links 24-, the controllever 23, and the adjustable feed back lever 44. The levers 25 and 44although shown separately have their left hand ends on the same axis sothat they move in synchronism. The

downward movement of the basic droop piston 39 causes a flow of oil fromthe space below the piston to the feedback circuit. This oil is .forcedinto the feedback receiver via connetion .45 and causes the piston 18therein to rise, compressing its spring 20. The increase of forceexerted by this spring causes the pressure under the feedback piston andin thefeedback circuit to rise. Asa result, the pressureentering throughconduit 54 into the space under the main pilot valve 9 rise-s causing anupward force on-thepilot valve, acting in the same direction as theflywheel force. 'This increase in force tends to cause the pilot valveto rise and shut off the flow of the control oil to the power piston 22.The rise in pressure created in the feedback circuit'by upward powerpiston movement exerts a force on the pilotvalve equivalent to a certainincrease in speed, hence, before further power piston movement takesplace, the speed must drop until equilibrium exists between the forceexerted by thechange in feedback pressure and the force reduction causedby the reduced rotational speed of the flyweights. Thus, if the feedbackdid not leak, a force would be exerted on the pilot valve systemdependent upon the power piston position and the ratio of the adjustablefeedback lever 44. Inpractice, leakage does exist, and in time, the feedback pressure would fall to atmospheric unless oil were supplied to thesystem to make up leakage. In this system, the leakage is made upthrough the permanent droop control valve restriction 28 which is in theaxial passage through the valve sleeve 30. When the governor is setisochronously the pressure setting of this valve 29 remains'constantirrespective of power piston position. This valve is connected .to thefeedback system via the integral adjust-mentrestriction 40 which allowsoil to flow from or to the feedback system at a predetermined rate,depending upon the pressure variation across this restriction. When anincrease of load occurs-the pressure in the feedback system will risedue to the displacement of the feedback system oil by the basic drooppiston into the feedback receiver. A pressure diiference, will thenexist across the restriction and flow will take place from the feedbacksystem, through the pressure control valve 29 to drain via connection46. As this flow occurs, the feedback receiver piston 18 will drop, thepressure decreasing proportionately until the pressure in the feedbacksystem is equal to the set pressure of the pressure control valve, andflow across the integral restrictor 40 ceases. In practice, the settingof the restrictor is adjusted to give optimum rate of return to a steadystate, dependent upon the characteristics of the prime mover. When thepressures have equalised, the forces acting on the pilot valve 9 willreturn to their original values and the equilibrium speed of thegovernor will return to its original value. 7

"Increase of Load (With Permanent Droop) When the governor is :set togive permanent droop, power piston movement causes a proportionalmovement of the permanent droop valve spring 27 altering the pressuresetting of the permanent droop valve 29. When an increase of loadoccurs, the power piston 22 moves upwards, the compression of spring 27is increased and the pressure output of the valve 29 increases; thus thepressure in the-feedback circuit-will attain an increased steady'statevalue. This increases the force acting on the pilot valve 9 causing theequilibrium speed to decrease. The amount of spaced variation withchange inload is varied by adjustment of the fulcrum 41 of the permanentdroop control lever'25, which, in turn, varies the relationship betweenpower piston movement and the pres'sur'echange of the permanent droopcontrol valve 29.

Decrease of Load Decrease of load causes the prime mover speed to rise.The flyweights 4 then move outwards releasing the control oil under thepower piston. The high pressure oil on the upper surface of the piston(supplied through connection 48) pushes it downwards to decrease thefuel input to the prime mover; the downward movement is transmitted tothe basic droop piston 39 causing the feedback pressure to drop, whichin turn tends to cause the pilot valve to close the oil port. Ifoperating with a permanent droop the pressure setting of the permanentdroop valve will decrease, resulting in a drop in feedback systempressure and an increase in the equilibrium speed of the governor.

Shut Down This is effected by draining the control oil by means of asolenoid-controlled valve (not shown). The valve used is of thepilot-operated type eliminating the need for a large solenoid.

When the solenoid is de-energized to shut down the engine the oil in thespace above this valve is allowed to escape. The spring force under thevalve pushes the valve upwards, cutting off the oil supply from the maincontrol ports to the underside of the power piston and draining the oilunder the power piston. The high pressure oil on the upper surface ofthe power piston pushes it downwards, cutting the energy supply to theprime mover. When the solenoid is energized the oil in the space abovethe valve is trapped and oil coming through the restriction will pushthe valve downward, opening the passage between the control port and thepower piston and so allowing the governor to operate in the normalmanner.

It is to be noted that in addition to operating isochroriously and witha positive droop, i.e. speed falling as load increases, the power unitcan be adjusted to give operation with a negative droop, i.e. speedrising as load increases. The term droop should therefore be taken inits broadest sense to cover both modes of operation.

The governor according to the invention has the following principaladvantages.

(1) The permanent droop control obtained by varying the steady statepressure in the feedback system eliminates the need for linkage betweenthe power piston and the main pilot valve, simplfying the constructionof I the governor.

(2) The use of the system allows,the power piston to be remote from theflyweight speed sensing mechanism and pilot valve.

(3) The use of the feedback system operating at above atmosphericpressure allows large transient feedback pressures to be used, so thatlarge forces are exerted on the pilot valve. This in turn allows largeflyweight forces to be used (obtained by running the flyweights at highspeed) and requires stifi speeder springs giving the flyweights a highnatural frequency and good response characteristics.

(4) The use of a feedback system operating at above atmospheric pressureeliminates troubles caused by aeration of the fluid in the feedbackcircuit (as would occur in systems where the feedback pressure becamesubatmospheric).

I claim:

1. Apparatus for controlling the speed of an engine in response tochanges in load on the engine comprising a governor responsive to enginespeed, means for varying the engine speed, means includ n a fluidpressure motor operably connected to said engine speed varying meanssure and having a pressure equalizing restricted connection to saidcontrol fluid pressure means.

2. Apparatus for controlling the speed of an engine in response tochanges in load on the engine comprising a governor responsive to enginespeed, means for varying the engine speed comprising a fluid pressureresponsive motor, means operated by the governor in response to a changein engine speed in one direction for applying a control fluid pressureto said motor for actuating said engine speed varying means to changethe engine speed in the other direction, feedback means actuated by saidgovernor operated means for opposing action of said governor operatedmeans for attaining a desired variable engine speed condition, saidfeedback means comprising a system wherein said control fluid pressureis varied by action of said governor operated means, and means forvarying the action of said feedback means comprising a restrictedpressure equalizing connection for gradually restoring the fluidpressure in said feedback means to equalization with said control fluidpressure. p

3. Apparatus for controlling the speed of an engine in response to loadchanges on the engine comprising a governor responsive to engine speedchanges, means for controlling the engine fuel supply, a power pistonoperably connected to said fuel control means, a source of control fluidpressure connected by conduit means to said power piston, a movablepilot valve in said conduit means operably connected to said governor sothat a change in engine speed acts through the governor to apply saidcontrol fluid pressure to the power piston to cause actuation of saidfuel control means to effect a change in engine speed opposing thatwhich acted through the governor, feedback means between the powerpiston and pilot valve comprising a fluid pressure transmitting systemcontaining a droop piston, means providing a pressure equalizingconnection between said conduit means and said'system for restoring thefluid pressure in said system to equal said control fluid pressure; andlinkage interconnecting the power and droop pistons so that actuation ofsaid droop piston by the power piston changes the fluid pressure in saidsystem applied to move said pilot valve, said means providing thepressure equalizing connection and comprising a passage having arestriction to control the pressure equalization time and a permanentdroop valve which is operably connected to said linkage and, opening inresponse to a transient pressure rise in said system, controls thepressure in said system.

4. Apparatus for controlling the speed of an engine in response to loadchanges on the engine comprising a governor responsive to engine speedchanges, means for controlling the engine fuel supply, a power pistonoperably connected to said fuel control means, a source of control fluidpressure connected by conduit means to said power piston, a movablepilot valve in said conduit means operably connected to said governor sothat a change in engine speed acts through the governor to apply saidcontrol fluid pressure to the power piston to cause actua tion of saidfuel control means to effect a change in engine speed opposing thatwhich acted through the governor, feedback means between the powerpiston and pilot valve comprising a fluid pressure transmitting systemcontaining a droop piston, means providing a pressure equalizingconnection between said conduit means and said system for restoring thefluid pressure in said system to equal said control fluid pressure; andlinkage interconnecting the power and droop pistons so that actuation ofsaid droop piston by the power piston changes the fluid pressure in saidsystem applied to move said pilot valve, and means for adjusting theconnection between said linkage and said permanent droop valve, saidmeans providing the pressure equalizing connection and comprising apassage having a restriction to control the pressure equalization and apermanent droop valve which is operably connected to said linkage and,opening in response to a transient pressure rise in said system,controls the pressure in the said system.

References Cited in the file of this patent UNITED STATES PATENTS2,364,115 Whitehead Dec. 5, 1944 2,623,504 Rodeck et al Dec. 30, 19522,734,490 Moulton Feb. 14, 1956 2,756,725 Parker July 31, 1956 2,762,384Rosenberger Sept. 11, 1956 2,769,431 Massey Nov. 6, 1956 2,769,432Massey NOV. 6, 1956

1. APPARATUS FOR CONTROLLING THE SPEED OF AN ENGINE IN RESPONSE TOCHANGES IN LOAD ON THE ENGINE COMPRISING A GOVERNOR RESPONSIVE TO ENGINESPEED, MEANS FOR VARYING THE ENGINE SPEED, MEANS INCLUDING A FLUIDPRESSURE MOTOR OPERABLY CONNECTED TO SAID ENGINE SPEED VARYING MEANS ANDA SOURCE OF CONTROL FLUID PRESSURE OPERATED BY THE GOVERNOR IN RESPONSETO A CHANGE IN ENGINE SPEED IN ONE DIRECTION FOR ACTUATING SAID ENGINESPEED VARYING MEANS TO CHANGE THE ENGINE SPEED IN THE OTHER DIRECTION,FEEDBACK MEANS ACTUATED BY SAID GOVERNOR OPERATED MEANS FOR OPPOSINGACTION OF SAID GOVERNOR OPERATED MEANS FOR ATTAINING A DESIRED VARIABLEENGINE SPEED CONDITION, AND TIME DELAY MEANS OPERABLE AFTER ACTUATION OFSAID FEEDBACK MEANS FOR VARYING THE ACTION OF SAID FEEDBACK MEANS, SAIDFEEDBACK MEANS COMPRISING A CONDUIT SYSTEM CONTAINING FLUID PRESSURE ATLEAST ABOVE ATMOSPHERIC PRESSURE AND HAVING A PRESSURE EQUALIZINGRESTRICTED CONNECTION TO SAID CONTROL FLUID PRESSURE MEANS.